This invention concerns a device for detecting and/or measuring the misconnection time in telecommunication networks, particularly MS-SPRING (Multiplexed-Shared Protection Ring) fiber optic telecommunication networks.
Hereafter the term xe2x80x9ctelecommunication networksxe2x80x9d will indicate signal conveying networks, either according to PDH (Plesiochronous Digital Hierarchy) standard or the more recent SDH (Synchronous Digital Hierarchy) standard. Anyway, the device for detecting misconnections according to this invention can be used in all telecommunication networks set up according to any standard, where misconnections can be generated even if simply due to an error of the managing software.
Telecommunication networks comprise units, located in the switched telephonic exchanges, designed as xe2x80x9cswitching matrixesxe2x80x9d, which establish circuits interconnection in order to put users in communication. Switching matrixes operate according to users"" requests or under direct control of the network manager, setting up the so-called semi-permanent connections. In addition to the above main purpose, i.e. traffic management according to connection requests, switching matrixes may also be used for a second purpose consisting in their use as units for automatic traffic re-routing should a connection interruption among the network nodes occur. Switching matrixes designed to perform said second function are typically contained in ADM (Add Drop Multiplexer) or xe2x80x9ccross connectsxe2x80x9d network nodes and they operate on semi-permanent connections.
A switching matrix has to ensure that in no way both a non requested connection or a connection which is different from the requested one, i.e. a misconnection, should be actuated. In this circumstance, in fact, damages may ensue for the user due to a loss of privacy or wrong operation of the processors automatically exchanging information through the switching matrix.
This danger is very high for a special communication network class called xe2x80x9cMS-SPRINGxe2x80x9d where, in the event of a connection interruption in the network nodes, the automatic traffic routing device may result in transient or permanent misconnections should the necessary precautions not have been taken, i.e. a correct and careful software and hardware design capable of implementing an automatic traffic routing. For this reason the automatic routing device of MS-SPRING networks is checked through a proper procedure, called validation procedure, after both design and its implementation.
The Standards dealing with MS-SPRING networks, e.g. ITU-T Standard G841 xe2x80x98CCITT Recommendation G 841, Draft, April 1995xe2x80x9d, underline that misconnections for said networks must be avoided.
However, so far no devices or procedures are known for detecting such misconnections and measure their duration to simplify and obtain an effective MS-SPRING network validation procedure.
As a matter of fact devices are known, generally defined as xe2x80x9cTest Pattern Generators/Checkersxe2x80x9d. Indeed, this definition refers to at least two devices, namely a transmitter connected to one inlet of the network and a receiver connected to one outlet of the network, which receiver is able to co-operate with the transmitter, i.e. the receiver decodes the special signal pattern introduced in the network by the transmitter and is aware of the special signals pattern to be received, so as to detect possible deviations and errors. xe2x80x9cTest Pattern Generators/Checkersxe2x80x9d are used for instance to check connection operation during validation tests of a telecommunication network.
Some of the means pertaining to the above category of xe2x80x9cTest Pattern Generators/Checkersxe2x80x9d are known as PRBSs (Pseudo Random Bit Sequences), such means generating sequences which are recognized by a proper receiver and used for auto-synchronizing purposes. However, a drawback is represented by the length of said patterns. PRBSs presently available on the market offer only three pattern lengths: 29xe2x88x921 bits, i.e. a signal with a 511-bit cycle, 215xe2x88x921 bits, i.e. a signal with a 32767-bit cycle, 223xe2x88x921 bits, i.e. a signal with an about 8-Mbit cycle. As a matter of fact, the misconnection time may be significantly shorter than the time required to transmit the pattern and recognize it at the receiver. Since said devices require more than one pattern length to engage and become aligned, it may happen that no misconnection is detected. Moreover, it should be noted that the Standards do not define a minimum misconnection time to be detected for MS-SPRING networks.
Short-length (16 bits) repeated-word generators are also known. However, said repeated word generators do not allow any autosynchronization with the receiver.
Moreover, both PRBSs and repeated word generators do not allow the achievement of the following information, which is crucial in the presence of misconnections, i. e. which pattern has been received instead of the expected pattern and which inlet it comes from.
In order to perform said operation with the PRBSs, it would be necessary for instance, to connect a receiver with each network outlet and check afterwards which receiver, instead of the expected one, has signaled the reception of the expected pattern.
Further, through known devices it is not possible to obtain information about the misconnection time, as these devices can only measure the loss-of-traffic time but not the time during which traffic is effectively provided. This prevents the duration of the real misconnection to be known from the reception of the all-ones signal representing the xe2x80x9csquelchingxe2x80x9d, or even from the noise reception.
Finally, the word length of known means cannot be changed, so that these means are not suitable to detect and measure the duration of misconnections under different conditions.
The present invention seeks to solve the above mentioned drawbacks and to provide a device for detecting and/or measuring misconnection time in telecommunication networks, specifically MS-SPRING networks.
Within this scope, it is the main object of this invention to provide a device for detecting and/or measuring misconnection time in telecommunication networks, which allows the detection of short-time misconnections and the origin of the signals, received as a consequence of said misconnections.
It is a further object of this invention to provide a device for detecting and/or measuring misconnection time in telecommunication networks provided with detecting and measuring means, which can be easily associated with the telecommunication network.
It is a further object of this invention to provide a device for detecting and/or measuring misconnection time in telecommunication networks, which allows the minimum detectable misconnection time to be changed.
It is a further object of this invention to provide a device for detecting and/or measuring misconnection time in telecommunication networks, capable of distinguishing misconnections from other events due to network malfunctions.
In order to achieve such objects, the present invention provides a device for detecting and/or measuring misconnection time in telecommunication networks and/or a method for detecting and/or measuring misconnection time and/or a test signal generator-transmitter and/or a test signal detector incorporating the characteristics of the annexed claims, which form an integral part of this description.